1. Field of the Invention
The present invention relates to a method of and apparatus for cleaning objects to be treated, such as semiconductor wafers or LCD (liquid crystal display) substrates etc., by immersing them in a cleaning liquid such as a chemical or a rinse, and sequentially drying the objects cleaned.
2. Description of the Related Art
During the process of fabricating a semiconductor device, a cleaning method is widely used to sequentially immerse objects to be treated or processed, such as semiconductor wafers or glass LCD substrates, into a processing tank filled with a processing liquid such as a chemical or rinse (cleaning liquid), to wash them.
A cleaning and drying apparatus of this type is provided with a drying device wherein a drying gas obtained from vapor of a volatile organic solvent such as isopropyl alcohol (IPA) is brought into contact with the surfaces of the wafers after the cleaning, the vapor of the drying gas condenses thereon or adheres thereto, and thus moisture on the wafers is removed, drying the wafers.
A conventional cleaning and drying apparatus that is known in the art as a typical example of this type of cleaning and drying apparatus is shown in FIG. 27. It comprises a cleaning tank A (cleaning chamber) which is filled with a chemical such as hydrofluoric acid and a rinse (cleaning liquid) such as distilled water, wherein objects to be treated, such as semiconductor wafers, are immersed in the chemical and cleaning liquid therein; a drying portion B positioned above the cleaning tank A; and a movement means such as a wafer boat C that holds a plurality of wafers W, such as 59 wafers W, and moves those wafers W into the cleaning tank a and the drying portion B.
Within the cleaning and drying apparatus of the above configuration, supply nozzles D that are connected selectively to a chemical source and a cleaning liquid source (not shown in the figure) are disposed within the cleaning tank A; drying gas supply nozzles E that are connected to a source (not shown in the figure) of a gas mixture of a drying gas such as IPA and nitrogen (N.sub.2) are disposed within the drying portion B; an aperture G that is freely enterable by a wafer conveyor chuck E is provided in an upper portion of the drying portion B; and a lid H is provided for opening and closing the aperture G.
In the thus-configured cleaning and drying apparatus, a plurality of wafers W, such as 50 wafers W, that have been transferred into the drying portion B by the wafer conveyor chuck F are received by the wafer boat C which is on standby within the drying portion B, the wafer boat C that has received these wafers W is lowered into the cleaning tank A to move the wafers W thereinto, and chemical processing is performed by supplying a chemical thereto and cleaning is performed by supplying a cleaning liquid thereto until it overflows. After the chemical processing and cleaning have been completed, the wafer boat C rises to move the wafers W into the drying portion B, and a drying gas (IPA+N.sub.2) is supplied from the drying gas supply nozzles E to bring the drying gas into contact with the wafers W, thus drying them. The dried wafers W are taken by the wafer conveyor chuck F that enters into the drying portion B and are conveyed outside, whereby one cycle of cleaning and drying is performed.
However, when the wafers W are transferred between the wafer boat C and the wafer conveyor chuck F that enters the drying portion B in the conventional cleaning and drying apparatus of this type, it is necessary to move the chuck portions sideways in order to enable the wafer conveyor chuck F to switch from a wafer holding state to a wafer non-holding state. It is therefore necessary to provide movement space within the drying portion B for the wafer conveyor chuck F, and the volume of the drying portion B must be increased accordingly. This increase in volume of the drying portion B not only leads to an increase in size of the apparatus, it raises further problems such as an increase in the amount of drying gas consumed therein and a lowering of the drying efficiency.
In addition, after the wafer boat C has risen to move the wafers W into the drying portion B of the above cleaning and drying apparatus, and during the drying process of supplying the drying gas to cause the drying gas to come into contact with the wafers W, the portions of the wafers W in contact with the wafer boat C that have been raised from within the cleaning liquid are in a state wherein drainage therefrom is bad and it is also difficult for the drying gas to come into contact therewith. Therefore, considerable time is required to dry the portions of the wafers W in contact with the wafer boat C, which causes a further increase in the consumption of drying gas, and this raises problems concerning decreased drying efficiency and increased cost. There are further problems concerning the danger of unevenness in the drying and reductions in yield.